Growth performances and feed utilization
Growth performances and feed utilization parameters of
E. suratensis after 90 days of growth trial are given in Table 2. The final body weight of the
insitu biofloc B1 and B2 fishes differed significantly with highest growth 53.26±0.18 and 57.90±0.06 respectively. The better feed utilization in terms of FCR (0.55±0.01), FER (1.83±0.01) and PER (1.93±0.01) were observed in (B2) compared to control and (B1). The
insitu biofloc reared fishes obtained higher survival rate compared to control. The highest biomass was observed in B2 (8260.97±0.05 g) and the lowest biomass was observed in control (5630.08 ± 0.05 g). The earlier studies reported that Biofloc technology (BFT) improves growth performance and feed utilization of cultured fish
(Hari et al., 2004; Azim and Little, 2008;
Kuhn et al., 2009; Ahmad et al., 2017; Luo et al., 2014; Zhang et al., 2016). Previous studies concluded that
insitu floc in various carbon sources served as an incremental food which continuously provide additional protein (EAA), polyunsaturated fatty acids, vitamins and minerals
(Avnimelech, 1999; Avnimelech, 2007; Azim and Little, 2008; De
Schryver et al., 2008; Luo et al., 2014).
Water quality parameters in in situ biofloc system
Water quality parameters were measured throughout the
in situ biofloc culture period as shown in Table 3. The temperature varied slightly throughout the
in situ floc production system and control tank further it varied between 26.5-31°C. DO concentration in
insitu biofloc tanks (B1 and B2) was within a range of 4.4-6.8 mg/l and did not show much variation throughout the experimental period, but it did fluctuate slighlty with increased biodiversity of floc associated organisms. While in control group, DO was in the range of 6.1-7.1 mg/l due to continuous exchange of water. In comparison to the control, the CO2 detected in the
in situ treatments was considerably (P<0.01) greater. Water pH was in the range of 8.3 to 8.5 in all
in situ biofloc production tank and 7 to 8 in control tank. Significantly (P<0.05) higher pH was observed in B1 and B2 than control. During the culture period ammonia concentration was in range of 0.001 to 0.008 mg/l in
insitu biofloc and 0.01 to 0.020 mg/l in control. Lower concentration of ammonia was observed in
in situ biofloc than control. Nitrite- ´100 nitrogen concentration was significantly (P<0.05) lower in treatments than control. The results of the water quality parameters on biofloc development with the jaggery as a carbon source was agreed well with findings of
Sakkaravarthi et al., 2015; Ruby et al., 2022; Elaiyaraja et al., 2020; Susitharan et al., 2021).
Digestive enzyme activity
The digestive enzymes
viz, amylase, protease and lipase activity were significantly affected by biofloc produced by
insitu manner. The results of digestive enzyme analysis were given in Table 4. Biochemical composition of the diet plays an important role in the digestive enzyme profile of fish and shrimp. The specific activity of digestive enzymes was significantly (P<0.05) improved in the current study when compared to control B2 and B1. Treatment B2’s increased digestive enzyme activity may have improved digestion and nutrition absorption, as evidenced by this group’s much greater (P<0.05) growth rate. The study by
Xu and Pan (2012) in biofloc based system reported the similar results in
P. vannamei. Growing performance may be enhanced by greater nutrient consumption brought about by higher digestive enzyme activity
(Ezhilarasi et al., 2019). Similarly, an enhanced digestive enzyme activity was reported in
L. vannamei Xu and Pan (2012),
P. monodon (Anand et al., 2013).
Nutrient composition (% wet basis) of Etroplus suratensis
The whole-body nutrient composition of
E. suratensis such as protein, lipid and ash are shown in Table 5. The highest crude protein in fish body was found in B2 (20.97±0.07) which differed significantly with C (15.43±0.27). The highest crude lipid recorded was (3.34±0.11) in B1, followed by B2 (3.21±0.05). Similar results with enriched nutritional value were also reported by
Ray et al., (2011); Xu and Pan (2012) reported that differences in proximate composition may affect nutritional value, sensory qualities and shelf-life of the fish.
Physiological immuno parameters of Etroplus suratensis
In the present study, fishes reared in
insitu biofloc treatments, the non-specific immune parameters NBT, serum lysozyme, myeloperoxidase (Fig 1,2,3) showed higher values as compared to control. Biofloc reduced the physiological stress in GIFT which agrees with the studies of
Verma et al., (2016) who reported the reduced levels of Cortisol and Glucose (Table 5) in
Labeo rohita when reared in biofloc systems. SOD and Catalase are two important enzymes in the cellular antioxidant defence system, dealing with oxidative stress. Lower levels of SOD and Catalase are indication for cell damage due to the accumulation of the high-level of free radical affecting the heath of fishes. The results from the present study revealed that the supplementation of
insitu biofloc increased SOD (Fig 5) and catalase (Fig 4) level in
insitu Etroplus suratensis than control. Similar studies were done by
Ruby et al., (2022); Menaga et al., (2019) and
Elaiyaraja et al., (2020). Increased bacterial pathogen killing ability of phagocytes can be inferred from increased respiratory burst activity which is a most important bactericidal mechanism in fishes.
Verma et al., (2016) observed an improvement in the immune parameters of Rohu fingerlings grown in tapioca-based biofloc. This could be connected to the fact that the culture animals’ consumption of biofloc improves their nutrition and activates the fish’s cellular defense mechanisms through phagocytosis and respiratory burst.
Disease resistance against Aeromonas infection of Etroplus suratensis reared in in situ biofloc system
In this study, fish injected with sterile saline (C-ve) showed no mortalities or pathological lesions, while those challenged with
A. hydrophila displayed pathological alteration on the third day post infection. The cumulative mortality rate (Fig 6) was considerably lower in the
insitu biofloc groups than control and the maximum relative protection (Table 6) was recorded in the B2, it was noted that all control fish died within 3-5 days post-challenge, while
in situ biofloc reared fish required a long time 5 to 9 days. The major organ manifestations were observed with the higher degree of infection in control
(Abraham et al., 2007). Since heterotrophic bacteria in the biofloc, created in the culture system produced immunostimulatory chemicals, the infection in B2 and B2 fish was shown to be less severe.
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